Magnetic and thermal induced ordering inV2O5 xerogel films

In this work we investigated the possibility of using magnetic fields and thermal treatments to induce ordering in V2O5 xerogels in film form. The xerogel was prepared by standard procedures. The films were prepared either by dip-coating or casting. X-ray powder diffraction, cyclic voltammetry as well as conductivity were used to monitor the changes. We found that the freshly made films are unstable, needing at least 48 h of rest at room temperature to have reproducible X-ray diffractograms, as well as conductivities. The changes are attributed to a decrease in film water content. Magnetic field treatments of several hours were observed to increase the ordering of the V2O5 ribbons, as well as the conductivity. For freshly deposited films the effects were larger than those in films left for a few days at room temperature. The electrochemical response of films exposed to magnetic fields did also show an increase in surface homogeneity. (C) 2002 Elsevier Science B.V. All rights reserved.